Brake boosters, often also referred to as brake apparatuses, serve to assist the foot pressure during application of a brake, with the pressure difference between the engine's intake pipe and the atmospheric outside pressure being used as an energy source. Such brake boosters are described in detail on pages 88-108 of the 9th edition of the Alfred Teves "Bremsenhandbuch" (Brake Handbook) published by Bartsch Verlag, Ottobrunn near Munich. As can be clearly seen from the cited literature on pages 96, 97 , for instance, brake boosters inter alia have an essentially plate-shaped working piston centrally held in a so-called control housing and guided by the same in the axial direction. The plate-shaped working piston serves to support a rolling diaphragm subdividing the cylinder into two working chambers which are acted upon by different pressures and which thus imply an axial movement of the working piston.
In regards to the aforementioned working pistons, a problem exists in supporting an essentially plate-shaped piston centrally in a plastic guide housing, and requiring the plate-shaped piston to be manufactured as thin as possible for weight reasons. On the other hand, it has to be considered that weight forces of up to half a ton can act on the plate-shaped piston and that the working piston must tolerate frequent application of movement in both directions and, hence, due to opposing actions of forces, cannot show symptoms of fatigue which might lead to the destruction of the booster.
Referring to the support of the plate-shaped piston in the guide housing in German patent application No. P 37 40 691, FIGS. 1-3, it is suggested that the inner end of the plate-shaped piston is bent in an essentially rectangular manner towards the rolling diaphragm so as to render an annular inner edge via which the plate-shaped piston radially supports itself on the controlling guide housing. In the axial direction, the inside of the plate-shaped piston is held by a surrounding projection on which the inner end is supported in the direction away from the diaphragm. On the opposite side, axial movement of the plate-shaped piston is prevented by the inner end of the rolling diaphragm which is held in a corresponding groove in the housing.
The present invention is thus based on a working piston and its object is to improve the central support of such working piston in a simple and cost-saving manner. In particular, the inventive working piston is to be manufactureable so as to be weight-saving.